On the capacity of picocellular networks

Abstract

Abstract-The orders of magnitude increase in projected demand for wireless cellular data require drastic increases in spatial reuse, with picocells with diameters of the order of 100-200 m supplementing existing macrocells whose diameters are of the order of kilometers. In this paper, we observe that the nature of interference changes fundamentally as we shrink cell size, with near line of sight interference from neighboring picocells seeing significantly smaller path loss exponents than interference in macrocellular environments. Using a propagation model proposed by Franceschetti, which compactly models increased interference in small cells, we show that the network capacity does not scale linearly with the reduction in cell size with standard frequency reuse strategies. Rather, more sophisticated resource sharing strategies based on beamforming and base station cooperation are required to realize the potential of small cells in providing high spectral efficiencies and quasi-deterministic guarantees on availability. Numerical results justifying these conclusions include Chernoff bounds on outage probability for random base station deployment (according to a spatial Poisson process), and simulations for deployment in a regular grid.

Demystifying 60GHz outdoor picocells

“…While this is indeed true at lower carrier frequencies [30], 60GHz's small interference footprint means that 60GHz picocells can be densely deployed with significant overlap but minimal interference, leading to a significant boost in spatial reuse. The reduced interference results from two factors: highly directional links that reduce interference between nearby users, and oxygen absorption and blockage from buildings that severely attenuate interference from distant cells.…”

“…Shrinking cell radii from several kilometers down to 100s (or even 10s) of meters is necessary to improve link quality and increase cell capacity. However, this approach is fundamentally limited by interference constraints for the carrier frequencies employed in today's cellular systems [30]. Specifically, at carrier frequencies of 1-5 GHz, physical form factor constraints put a hard limit on the number of antennas that can be accommodated on a picocellular basestation and a mobile device.…”

“…Specifically, at carrier frequencies of 1-5 GHz, physical form factor constraints put a hard limit on the number of antennas that can be accommodated on a picocellular basestation and a mobile device. Thus, even MIMO technologies can only mitigate interference to a limited degree, and picocell systems based on low carrier frequencies (LTE, WiFi, TV whitespaces) are unlikely to ever deliver the capacity increase we need [30]. The Promise of mmWave.…”

Interference Management and Capacity Analysis for mm-Wave Picocells in Urban Canyons

“…It is worth emphasizing yet again the contrast between our results and those at lower frequencies. As we increase cell density, interference can become a fundamental limiting factor at lower carrier frequencies [19]. Our analysis shows that this is not the case for mm-wave frequencies: the narrow beams yield large gains in spatial reuse, which translate to orders of magnitude capacity increases.…”

PCach: The Case for Pre-Caching your Mobile Data

“…This spectacular improvement is probably the only thing clear about 5G -getting there is still subject to intense debate in academia and industry. Nevertheless, there is general agreement that the increase in performance will be achieved through a combination of Millimeter Wave (mmWave) [1,18], ultra-densification [4,17], massive multiple-input, multipleoutput (MIMO) [13,14] and edge caching [5]. All these solutions, however, require fundamental changes to the architecture of mobile networks and are still years away.…”